How would an opera at the Sydney opera house be like without the expertise of the conductor? With the violins, harps, flutes and trumpets playing according their own accord, there would be nothing but clamor. Now, in a microprocessor, if the ALU, memory, other units were to perform their activities without a grand orchestrator- the clock, we could have the result of 1 + 1 as 3. That pretty much sums up the role of the clock and its significance in the current concurrent world of logic circuits. While the clock acts as a conductor in the opera of the sequential logic, this clock is also a source of concern for the system. With its own demands of timing constraints, metastability, clock skew and highest power consumption compared to most other components on the chip, the clock seems a necessary evil.
But the long forgotten and newly revived domain of asynchronous VLSI systems is a field that despite having its own share of problems, promises to overcome most of the problems faced by synchronous systems today. This paper looks into the working of the clocked systems in section 1 and traces the history of asynchronous VLSI systems in section 2. The advantages and the challenges in the field and the current state of this technology are looked at in section 3. We discuss the design of an asynchronous core for digital watermarking of videos that we are currently working on in section 4. Section 5 discusses the future possibilities of integration of asynchronous and synchronous systems and section 6 gives an insight into the recent developments in this field.